[(2R,3S,6S)-3-Acetyloxy-6-(1-phenyl-1H-1,2,3-triazol-4-yl)-3,6-dihydro-2H-pyran-2-yl]methyl acetate

In the title compound, C18H19N3O5, the 3,6-dihydro-2H-pyran ring adopts a half-chair, distorted towards a half-boat, conformation with Q T = 0.5276(14) Å. The benzene ring is twisted out of the place of the triazole ring [dihedral angle = 23.54 (8)°]. In the crystal, supramolecular layers in the ac plane are formed through C—H⋯O and C—H⋯π(triazole) interactions. These stack along the b axis being connected by C—H⋯N contacts.


Comment
The chemistry and biological activity of C-glycosides has experienced increased attention due to their structural similarity to carbohydrates but also due to their resistance to metabolic processes. Such attributes may lead to improved biological profiles as compared to their O-analogues (Ritchie et al. 2002;Hanessian & Lou, 2000;Hultin, 2005;Zou, 2005). In addition, C-glycosides have also been found embedded in the structure of several bioactive natural products (Nakata, 2005;Nicolaou et al. 2008), and served as chiral building blocks for the stereoselective synthesis of optically active compounds (Somsak, 2001).
The title compound, (I), Fig. 1, was prepared in connection with on-going research into the synthesis of C-glycosides.
The absolute structure was confirmed experimentally and shows the chirality at the C9, C12 and C13 atoms to be S, S, and R, respectively. The dihedral angle between the phenyl and the triazole ring is 23.54 (8) °. The 3,6-dihydro-2H-pyran ring has a distorted half-chair conformation with the O1 atom lying 0.6127 (16) Å above the plane defined by the C9-C13 atoms In the crystal packing, the molecules are linked through C-H···O, C-H···N and C-H···π interactions, Table 1. The short C-H···O contact, involving the trizaole-C-H and the carbonyl-O4 atoms, leads to chains along the b axis. These are linked along the a direction into a 2-D array via C-H···π interactions that occur between the methine-C-H and the ring centroid of the trizole ring. Fig. 2. The zigzag layers are stabilized by a number of weaker C-H···O interactions (Table 1) and stack along the b axis with the most significant interaction between them being of the type C-H···N, Fig. 3.

Experimental
The reaction was carried out in a two neck 25 ml flask under a nitrogen atmosphere. To copper iodide (96 mg, 0.5 mmol) was added a solution of ((2R,3S,6S)-3-acetoxy-6-((trimethylsilyl)ethynyl)-3,6-dihydro-2H-pyran-2-yl)methyl acetate (155 mg, 0.5 mmol) in 2 ml of THF, a solution of phenyl azide (71.4 mg, 0.6 mmol) in 3.5 ml of THF, and finally, drop wise, tetra-n-butyl ammonium fluoride (TBAF) (0.6 ml, 0.6 mmol) was added. The mixture was sonicated in an ultrasound bath for 90 minutes. The reaction mixture was then quenched with 20 ml of ammonium chloride and extracted with 3 x 15 ml of ethyl acetate. The organic phase was washed with 3 x 15 ml of water, dried with MgSO 4 and then the solvent evaporated in a rota-vapor. The product was purified through a chromatographic column using ethyl acetate/hexane (1:3) as the eluent.
Crystals were grown by slow evaporation from a solution of 15% of acetyl acetate in hexane at 293 K; M.pt: 379-382 K.